1. Field of the Invention
The present invention relates generally to a method and apparatus for rapidly chilling a flow of a food substance such as ground meat or the like as the food substance flow is conveyed along a path of travel that extends substantially axially through a generally cylindrical housing assembly. More particularly, the present invention relates to the use of an auger-type conveyor that has a housing assembly with coaxially-arranged casings which define an inner chamber wherein an auger rotates to convey a flow of food substance from an inlet to an outlet, and a surrounding refrigerant chamber to which liquid cryogen is supplied, and from which cryogen that has evaporated to form a gas is discharged. The temperature of the discharging gas is monitored and is utilized in regulating the supply of liquid cryogen to the refrigerant chamber. By regulating the supply of liquid cryogen so that the discharging gas has a temperature that lies within predetermined limits, the temperature of the food substance that discharges from the apparatus is likewise maintained within desired limits that may be required to permit further processing of the food substance.
2. Prior Art
It is known to utilize auger-type conveyors, sometimes referred to as "screw-type" conveyors, to convey a flow of a food substance such as ground meat along a predetermined path of travel, and to expose the flow of food substance directly to various types of cryogenic materials to rapidly cool and/or to quick freeze the food substance. However, direct exposure of certain comestibles such as ground chicken meat to cryogenic materials such as liquid or solidified carbon dioxide often has been found to have a deleterious effect on the quality of the food substance. For example, some direct exposures of ground chicken meat to liquid carbon dioxide have been found to enhance the tendency of the meat to serve as a host media for bacterial growth, i.e., to promote the onset of rancidity. Especially with such comestibles as ground chicken meat, direct exposure to cryogens such as liquid or solidified carbon dioxide have been deemed to constitute an inappropriate means of diminishing the temperature of the meat from a typically encountered processing temperature of 70.degree.-80.degree. F. to a packing temperature of 40.degree. F. or below.
Other proposals have called for the use of an auger-type conveyor for conveying a flow of food substance from one location to another during processing, with a limited degree of concurrent refrigeration being provided by surrounding a housing of the auger-type conveyor with various forms of refrigeration units, or by incorporating refrigeration coils or refrigerant flow paths into side wall portions of the housing. However, such proposals typically have suffered from such drawbacks as failing to provide adequate refrigeration capacity to rapidly diminish the temperature of the flow of food substance to desired degrees as the flow is conveyed along a travel path that is defined by the auger, failing to effect an adequately uniform cooling of the food substance as it is conveyed along the travel path defined by the auger, and failing to provide refrigeration techniques that can adequately accomodate and properly adjust for typically encountered variations in the rate of flow of the food substance that is being fed into the conveyor, and/or typical variations in the character, consistency and temperature of the food substance that is being fed into the conveyor. Previously proposed refrigeration systems for use with auger-type conveyors have been undesirably expensive to purchase and maintain due to their complexities of construction, have been undesirably expensive to operate in view of the ineffective manners in which they employ refrigerant, and have not been as responsive or as adjustable as has been needed to accommodate variations in flow rates, character, consistency and temperature of such comestible products as are typically fed along auger-defined flow paths.